The present invention relates to a high frequency connector adapted for interconnecting a microstrip circuit and an external circuit and, more particularly, to a connector structure suited to connect transverse electromagnetic mode (TEM) waves which lie in a 0.3-30 GHz frequency band.
A microstrip substrate is an implementation recently developed for the circuit construction of various equipments of the kind which use the microwave band. One of the major problems with a microstrip substrate is the interconnection between the substrate and an external circuit. FIGS. 1 and 2 show different prior art connectors which may be used to interconnect a conductor section of a microstrip substrate, which is received in a housing, to a coaxial cable. In FIG. 1, a connector 10 is fit in a bore 18 formed in a wall 16 of a housing 12, which accommodates a microstrip substrate 14 therein. Specifically, the connector 10 comprises a shell 20 provided with a flange 22 and a male screw 24 which is to mate with an external circuit, an intermediary insertion member 26 coupled in the shell 20 and in the bore 18 of the wall 16 of the housing 12, and a center conductor 28 supported by an insulator 30 inside the hollow shell 20 and insertion member 26. Before mounting the connector 10 to the housing 12, the microstrip substrate 14 is fixed in a predetermined position inside the housing 12. Then, the insertion member 26 of the connector 10 is inserted into the bore 18 of the housing 12, then a center conductor pin 34 provided with a connecting ribbon 32 beforehand is inserted into a slitted portion 28a of the center conductor 28 from inside the housing 12, and then the ribbon 14 is soldered to a corresponding conductor portion on the substrate 14.
In FIG. 2, a prior art connector 36 of the type using a glass bead 38 is shown. The bead 38 comprises a tube 39 made of metal and a center conductor pin 40 which is fixed in place by glass 42 at the center of the tube 38. In assembly, the bead 38 is inserted into the housing 12 to align with a conductor on the microstrip substrate 14, then solder is poured into a bore 44 provided in the upper end of the housing 12 so as to fix the bead 38 in place, then the center conductor pin 40 and a conductor portion of the substrate 14 are soldered to each other, and then the connector 36 is screwed into the housing 12.
The problem with the connector configuration shown in FIG. 1 is that due to the substantial inductive impedance of the ribbon 32 the voltage standing-wave ratio (VSWR) is high at frequencies higher than several gigaherzs. Another problem is that the connection of the ribbon 32 requires extra steps. Meanwhile, the connector configuration shown in FIG. 2 is disadvantageous in that a considerable number of steps are necessary for the bead 38 to be fixed in place by solder, which is poured into the bore 44 of the housing 12, and in that the manipulation for replacing the microstrip substrate is intricate. In addition, both the connectors shown in FIGS. 1 and 2 are expensive to produce and need expensive structural parts.